Open-source pioneer and Novell Vice President Miguel de Icaza Thursday for the first time publicly
slammed his company's cross-patent licensing agreement with Microsoft as he defended himself against lack of patent protection for third parties that distribute his company's Moonlight project, which ports Microsoft's Silverlight technology to Linux.

if you read his full reasoning on it here http://tirania.org/blog/archive/2007/Jan-30.html, you will see that his opinion on OOXML is well reasoned, and coming from his position as the creator of the most used spreadsheet in the free software world, not as the VP of a company which has partnered with MS.